G95 G-Code Explained: Feed Per Revolution for Precise Turning and Threading

G95 G-Code Explained: Feed Per Revolution for Precise Turning and Threading

G95 is a G-code that changes the way feedrate is interpreted in CNC programs. Instead of units per minute (like in G94), it uses units per spindle revolution — making it ideal for turning, threading, and operations that need synchronized motion with spindle speed.

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📘 What Does G95 Do?

When G95 is active:

• F feedrate is interpreted as mm/rev or inch/rev
• Feed advances proportionally to spindle RPM
• Crucial for operations like single-point threading and rough turning

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🔁 G94 vs G95 Comparison

Mode	Feedrate Unit	Best Use Case
G94	mm/min	Milling, general machining
G95	mm/rev	Turning, threading, lathes

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🧪 Example: Rough Turning with G95

G95           ; Feed per revolution mode
G96 S200 M03  ; CSS mode: 200 m/min
G00 X50 Z2
G01 Z-50 F0.2 ; 0.2 mm per revolution

• Feed rate adapts to changing RPM
• Ensures consistent chip thickness and surface finish
• Especially important when cutting near the spindle center (diameter changes)

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🔩 Threading Example with G95

G95
G97 S600 M03
G76 P020060 Q100 R0.05
    G76 X20 Z-25 P1000 Q200 F1.5

• F1.5 = 1.5 mm thread pitch
• With G95, feed and RPM are locked together
• Allows perfect thread tracking per spindle revolution

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⚠️ Important Notes

• G95 is modal (stays active until changed)
• Switch back to G94 for milling or rapid moves:

G94 ; Feed per minute mode

• Some controllers (especially lathe-specific) default to G95 at startup

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🔧 Tip: Use G95 with G96 (Constant Surface Speed)

Perfect for turning large diameters:

G96 S180 M03  ; CSS ON
G95           ; Feed per revolution

This keeps surface speed AND feedrate consistent throughout the cut.

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🧠 Summary

Feature	G95
Feedrate Unit	mm/rev or inch/rev
Best for	Turning, threading, boring
Benefits	Uniform chip load, thread sync
Modal?	Yes
Switch Off	With G94

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✅ Best Practices

• Always specify G95 explicitly at program start on turning centers
• Match F values carefully to material & tool
• Always simulate threading cycles with G95 ON
• Cancel with G94 when switching to mill-style operations

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▶️ Coming Up: G96 vs G97 – Constant Surface Speed vs Fixed RPM in CNC Turning